1. Field of the Invention
The present invention is directed, generally, to an assembly having a multi-layer dielectric and its method of manufacture.
2. Description of the Prior Art
Dielectric layers are very important in the production of integrated circuits because they provide an insulating barrier between conductive layers and protect the underlying layers from such things as impurities, moisture, and stress related impacts. It is desirable that the dielectric layer fill the spaces between the parallel conductors. Otherwise, voids left between the conductors can cause the circuit to fail for a variety of reasons, such as latent defects caused by impurities and moisture. Voids between the parallel conductors can also cause the circuits to fail due to electric shorts between structures formed subsequent to the dielectric deposition. Furthermore, certain dielectric characteristics cause undesirable effects, such as “cross talk” between parallel conductors of current. Accordingly, the quality of the dielectric layer is a factor in the reliability and performance of the integrated circuit.
FIG. 9 illustrates a dielectric formation problem known in the art known as “shadowing”, wherein some areas in the openings 118 between the structures 112 are more prone to developing voids 110 during the formation of the dielectric layer 102, thereby resulting in a less effective integrated circuit. Various attempts have been made to reduce or eliminate shadowing, and thereby improve the overall quality of the dielectric layer.
It is known to form multiple dielectric layers to provide benefits not available with a single dielectric layer to improve dielectric quality. However, several deficiencies exist in the prior art. For example, it is known to form a multi-layer dielectric having an adhesive coating between each dielectric layer. The adhesive coating, however, introduces an additional step in the fabrication process, which reduces manufacturing efficiency and increases costs. Also, it is known to form three layers of dielectric material having varying degrees of quality and thickness, with the third top layer being relatively thick. Formation of a three layered dielectric, however, requires significant manufacturing time and cost, particularly when thickness and high quality are necessary characteristics of one of the layers.
Accordingly, the need exists for an improved multiple layer dielectric providing good gap-fill characteristics, whereby only two layers are needed, and an adhesive layer is not needed.